This R21 proposal is submitted in response to the NIDA RFA DA-04-009. The primary goal of this study is to examine the influence of experimentally-induced negative affect on impulsivity and risk taking among adolescent experimental smokers and adolescent never-smokers. Negative affect may cause impulsivity and risk taking to increase. Adolescents who become particularly impulsive and prone to risk taking under negative affect conditions may be particularly likely to experiment with cigarettes, leading to increased smoking during later adolescence or early adulthood. This study (N=110) will use a 2 (adolescent experimental smokers vs. adolescent never-smokers; between-subject factor) x 2 (negative affect vs. neutral affect; within-subject factor) design to examine the hypothesis that increases in impulsivity and risk taking under negative affect conditions will be more prominent among adolescent experimental smokers than never-smokers. Film clips will be used to induce negative affect. Dependent measures will include (a) the degree to which delayed rewards are discounted, (b) performance on a computerized risk taking task, and (c) ability to inhibit prepotent responses. Previous studies of adolescent smoking have typically used self report questionnaires to assess impulsivity and risk taking. Therefore, the use of behavioral measures in this research represents a significant innovation. By including equal numbers of males and females in this study, we will also be able to address interactions between gender and smoking status. Female smokers may be particularly likely to become impulsive and risk prone under negative affect conditions. The results of this study may identify behavioral and emotional processes underlying early episodes of adolescent smoking. The long-term objective of this research is to improve adolescent smoking prevention and cessation efforts by gaining a better understanding of the mechanisms leading to smoking in this population.